What is the difference between using echo and return in PHP functions, and when should each be used?

In PHP, the main difference between using echo and return in functions is that echo is used to output data to the screen, while return is used to return a value from a function. If you want to display something directly to the screen, you should use echo. If you want to pass a value back to the calling code, you should use return.

// Using echo to output data to the screen
function displayMessage($message) {
    echo $message;
}

displayMessage("Hello, World!");

// Using return to pass a value back to the calling code
function addNumbers($num1, $num2) {
    return $num1 + $num2;
}

$result = addNumbers(5, 3);
echo $result; // Output: 8